Problem Running Demo Program on nRF91X Thingy

[rblackner]

Hi,

I recently started working with the nRF9151 DK and was able to run the initial demo programs without any issues. To continue testing, I picked up a Thingy:91 X, but it consistently fails to attach to the LTE network (yellow LED flashing).

What I’ve tried so far:

• Registered all SIM cards

• Connected using nRF Connect for Desktop → Quick Start → Start Prototyping

• Multiple power cycles and tests with different SIM cards

• Reprogrammed the device via Quick Start

Despite these steps, the device still gets stuck when searching for LTE.

Question:
What are the recommended next steps to debug LTE attach on the Thingy:91 X? Are there specific AT commands, APN settings, or modem trace procedures I should use to narrow down the issue?

Thanks in advance for any guidance!

[SoTXhelp]

Hello Reily,

Sorry to hear that you are having issues connecting with the Thingy91X. 

I generally run AT+CEREG=5 to turn on notifications related to network connections. If I am mobile this will update me when I am moving between cells or if I drop from coverage. This automatically updates on changes to the tower connection.

AT%CESQ=1 will auto update on RSRP (Signal quality)

I suggest running Cellular Monitor so that you can capture a trace of the connection. This will provide much more diagnostic information for us to evaluate what is happening. 

Were you successful connecting with the nRF9151DK board with a SIM? If so, use the same SIM on the Thingy91X and try again. 

It can take over 15 minutes for the SIM to update to a new local profile the first time it is uses. Once configured it should attach rapidly.

We are wanting to see +CEREG indicate 5,1 (home network) or 5,5 (roaming network).

In Nordic nRF Connect for Desktop you would open cellular monitor, select the Thingy91X. Then select start. Using a program from QuickStart automatically enables trace capture. You should see the indication at the bottom of the screen where the file size should be incrementing. This is a binary file. It should be shared here so we can see what is happening in your network.

Regards,

Don

[rblackner]

Hi,

I’m testing the Thingy:91 X alongside an nRF9151 DK. On the DK, I can attach to LTE without issues using multiple SIMs, but when I move the same SIMs over to the Thingy:91 X, the device hangs indefinitely with the yellow LED flashing (searching for LTE).

What I’ve tried so far:

• 4 different SIM cards (2× Conexa, 2× Onomondo)

  • All work fine in the nRF9151 DK

  • None attach when inserted in the Thingy:91 X

• Followed the Quick Start flow in nRF Connect for Desktop (Start Prototyping)

• Power cycling, reprogramming via Quick Start, and trying different APN settings

• AT commands over UART are accepted

• Tested with and without band locks (no change)

Cellular Monitor behavior:

• On the DK, I captured a modem trace and did see an error (attached) perhaps this might help.

• On the Thingy:91 X, Cellular Monitor seems to get stuck on the initial “TRACE” step and does not progress.

Question:
Since the SIMs and network attach correctly on the DK, what could prevent the Thingy:91 X from attaching? Are there extra steps (firmware alignment, bridge firmware, antenna configuration, etc.) that I may have missed in setup?

Attachment:

trace-2025-08-19T18-06-59.190Z.mtrace